Pulse-transmitting device



April 3, 1951 A. MAMOR PULSE TRANSMITTING DEVICE 3 Sheets-Sheet 1 Filed July 1, 1948 Attorney April 3, 1951 A. MAMOR 2,547,034

PULSE TRANSMITTING DEVICE Filed July 1, 1948 3 Sheets-Sheet 2 Altorney April 3, 1951 A. MAMOR PULSE TRANSMITTING DEVICE 3 Sheets-Sheet 3 Filed July 1, 1948 Attorney Patented Apr. 3, 1 951 UNITED STATES PATENT OFFICE PULSE-TRANSMITTING DEVICE Armand Mamor, Antwerp, Belgium, assignor to International Standard Electric Corporation,

New York, N. Y., a corporationv of Delaware Application July 1, 1948, Serial No. 36,392 In the Netherlands August28, 1947 8 Claims.

This invention relates to a signalling system. More particularly it deals with a system for transmitting and receiving a predetermined number of undulations of an alternating current wave which number may be varied according to the signal to be transmitted. For example, the alternating current wave may be within the voice frequency range and the number of its undulations which are transmitted may correspond to the dialling pulses for fast dialling over long distances.

Previously, the transmission of telephone dialling pulses over long distances was made by the transmission of direct current pulses or by their modulation on an alternating current carrier wave. These systems had the disadvantage that the transmission of the dialling pulses was not much faster, if at all, than the time it took to manually operate the telephone dial for sending them.

It is an object of the present invention to materially increase the speed of sending dialling pulses by counting the undulations or number of half wave lengths of an alternating current wave within the voice frequency range wherein said number of undulations corresponds to the number of dialling pulses to be sent for each digit. For example, if eight pulses are to be sent, four positive and four negative undulations are counted and transmitted over the line with a slight pause before the next digit number of undulations is transmitted.

Another object of the present invention is to transmit and receive freely numbers of pulses Without the employment of mechanically moving apparatus to produce the pulses other than, for example, a push button, for the selection of desired number of' pulses to be sent.

Another object is to transmit dialling pulses for long distances over telephone lines without the employment of special and separate relaying means at repeater stations, since the dialling pulses are within the voice frequency range.

Another object is to produce a special electronic circuit for switching on and off the positive and negative half periods or Wave lengths ota voice frequency wavewithin a given narrow time interval or phase angle of the half-wave form.

In accordance with this invention, a system for; transmitting" and receiving 'a predetermined number of half waves of alternating electric mitter or a line by an electronic switching circuit controlled to switch Within such a narrow phase angle of each half wave period, so that at least a suflicient amount of the period will be transmitted to produce a full signal indication. The number of half waves to be transmitted is controlled by a preset means, such as push-buttons, which control the starting of the electronic switchand by means of a counting chain which controls the electronic switch to stop trans'rnis sion when the preselected number of half waves have passed through said switch. The receiving stationalso' comprises a similar counting chain which may control a group of relays corresponding to each half wave or undulation received from the transmitting station. The frequency of the alternating energy or speed at which these half waves or pulses may be transmitted is limited only by the speed of operation of the counting chain and of the relays which restore the transmitting circuit for the transmission of the next train of undulations. Practically speaking, for alternating electric waves within the voice frequency range a group of ten undulations may be sent in about of a second.

The above mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself'will' be best understood, by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a schematic wirin diagram of a transmitte'r circuit of one embodiment of this invention adapted to a key-set telephone dialling system;

Fig. 2 is a schematic wiring diagram of one embodiment of a receiving circuit for receiving the signals sent by a circuit similar to Fig. 1;

Fig. 3' is a graph of a waveform useful in explaining the operation of the circuit shown in Fig. 1.

Referring to Fig". 1, the transmittin station circuit may comprise a series of push-buttons I through ID for transmitting ten different signals, namely from one to ten successive half waves of an alternating current wave over the voice frequency telephone lines" I I from the constant alternating electric energy (A. C.) source I2. These push buttons are directly connected to an electronic counting: chain circuit l3 which controls an'electronically controlled static switching circuit l4 between the lines H and the A. C. source'l2'. Thus,- when any one of the push buttons (I tolm isoperated, contacts l5 are closed which energize the starting relay I5 connecting A. C. source I2 through contacts I! to the primary of input transformer I8. Simultaneously, with the closure of contacts H the following other contacts are closed: self-holdin contacts I9, contacts for energizing the restoring relay 2 I, and contacts 22 to maintain the ground connection to the counting chain circuit I3 and switching circuit I4. A battery 23 or other low tension source may be provided for the operation of these two relays. H

The transformer I8 together with transformer 24 and the circuit between their respective secondary and primary windings including rectifiers 25 form a static switch in which the relative 'voltage between points 26 and 21, on each side,

of the rectifiers at the mid-points of said secondary and primary, control the conductivity and non-conductivity of the circuit between said transformers. Each transformer I8 and 24 is .provided with a tertiary Winding 28 and 29 which are respectively connected to circuits which control the relative voltages at points 26 and 21 to open and close the static switch. The secondary of transformer 24 is connected to the line I I. The tertiary winding 28 of input transformer I8 is connected to a control valve, such as cold cathode tube 30, in the switching circuit I4. The tube 30 fires when the positive crest 3| (see Fig. 3) of A. C, wave 32 from source I2, rises above the breakdown voltage level of tube 30 (represented by line 33) when said A. C. potential of source I2 is superimposed on the constant D. C. bias or polarization voltage (represented by dotted line 34) from the high tension (H. T.) source 35 through potentiometer 36. The firing of tube 30, thus raises the voltage of point 26 sufiiciently above that of point 21 to permit both the positive and negative A. C. pulses from source I2 to pass the rectifiers 25 to the output transformer 24 and on to the line I I.

In order to stop the transmission of the wave at the desired point, each undulation of the wave passing through the rectifiers 25 is taken from the tertiary winding 29 of transformer 24 through rectifiers 3'! and 38 to operate in succession each one of the valves, such as cold cathode tubes 39 through 48, in the counting chain circuit I3. Through the push button (of the group I to Ill) which was operated to start the circuit, the firing voltage from its corresponding tube in the counting chain I3, is directly connected through low resistance sensitive relay 49 and rectifier as to the point 2'! to raise its voltage now above that of point 26, preventin further conduction of energy through rectifiers 25, and accordingly preventing further transmission of any undulations of the wave from the source I2 .on to the line I I. This sensitive low resistance relay 49 open its contacts 5I breaking the holding circuit'for the starting relay I6 to de-energize this relay before the restoring relay 2| is released. If desired, a sensitive helping relay (not shown) may be employed for the operation of relay 49 and opening of contacts 5I in Fig. 1. The restorin relay 2 I, however is not released until all the cold cathode tubes have had time to deionize and the pressure of the finger on the selected push button of the group I to ID, has been removed and the con-' tacts I5 have been opened due to action of spring 52 to break the circuit from ground through contacts I5, lines 46 and 53, self-holding contacts 54 of relay 2I and relay 2I to the low tension source 23. If desired, however, the operation of the contacts I5 may be controlled electrically by a slow release relay or other means well known to those in the art (not shown) After these operations the circuit is again restored by dropping both the voltages at points 25 and 2'3 to their initial values in which the voltage at 21 is slightly higherthan at 25, and the circuit I4 is again non-conductive to be re-initiated upon the operation of another push button of the group I to Ill. The total operation of this circuit is suificiently fast so that an operator in pressing one of the push buttons with the finger, as fast as manually possible, still retains the push button contact closed for a sufficient time for all of the above operations to take place.

In order to ensure that a substantial portion of the first pulse to be transmitted will be of suflicient duration and magnitude to operate the first tube 38 of the counting chain-circuit I3,

a. delay comprising resistor 55 and condenser 56 are connected in parallel between the high tension source and-thepoint 26. This delay is of such duration that if the contacts I! were closed at the time indicated by the vertical straight line 51 in Fig. 3, the first undulation of the Wave 32 would not be transmitted to the counting chain, because of the duration of the delay indicated by distance 58. Thus, the first pulse to pass to the countin chain, is the next and negative pulse or undulation 59 shown in Fig. 3. The amount of the delay 58, the level of the D. C. polarization voltage 34 and peak of the positive undulations of 'wave 32 are so chosen that if the contacts I1 are closed at a point indicated by line 60,- just at the last instant to fire the tube 30, then after the delay 6| (same as 53) there will still pass a sufficient amount of the following negative undulation 62 to ensure the firing of the first tube of the-counting chain circuit, both at the sending station and at the receiving station (Fig. 2).

This next and negative pulse (59 or I52) then passes its corresponding rectifier 25' through the transformer 24 on to the line II as well as from the tertiary winding 29 through the rectifier 38 to fire the first tube 39 of the counting chain I3 (rectifiers 63 may be inserted to suppress unwarranted polarity pulses on the counting chain circuit I3). This tube 39 is the first and only tube to be fired by this pulse or half wave in that it has applied to its control anode a polarizing voltage from the potentiometer comprising resistors 64 to charge condenser 65. Similarly for the pulses of the opposite polarity, there is provided a potentiometer comprising resistors 65 charging condenser 6'5 to polarize the second tube 45. The cathodes of each of these tubes are directly connected to the contacts of push buttons I-lfl. The firing of each tube passes on a polariza tion voltage to the control anode of the following tube through resistors 68 charging the corresponding following condenser 69 and so on, through the counting chain from one side to the other until the tube that is fired has its cathode connected through a closed corresponding push button contact I to Ill. There are provided condensers I0 after the first two tubes 39 and 40 of each polarity, in parallel with and between the cathodes of the following tubes to prevent the firing of the following tube by the voltage surge from the cathode of the previous tube, which might bring the control anode to the breakdown potential before the next pulse reaches it. There'- fore, both cathodes rise together in voltage as the previous tube fires so that the following tube will not also fire because its cathode was ata relatively lowervoltage. .Furthermore, each bf the cathodes of each tube of thecounting chain circuit I3 are connected through resistors II which limit the current and act as rheostats to keep the cathodes connected at a potentialwhich is a safe distance below the break-down voltage of the tubes. The firing of the selected tube then directly applies the firing potential of that tube through conductor '52, relay 49 and rectifier 50 to thepoint 2'I raising its potential to a level above that of point 26, and simultaneously blocking the passage of further pulses through the rectifiers 25. The rectifier 50 separates the point 2'! from the cathode of the selected or marked tube of the counting chaincircuit I3, so that the voltage at point 21 will not raise the cathode voltage of the marked tube, and. thereby make it less sensitive to the action of the last pulse.

2 Both points 2% and 21 are maintained slightly below the maximum potential which maybe applied to them, by means of resistors I3 and I4 respectively, the resistor I3 being greater than 14 so that in rest condition the potential at point 21 will be above that of point 25 and the static switch will be non-conductive. In order to ensure that the last pulse is completely transmitted, a delay comprising resistor 15 and condenser I6 (similar to the delay of resistor 55 and condenser 56) are connected in parallel between the high tension source and the point 21 topermit the transmission of substantially all of the pu se since the last tube is fired by the leading edge of the last pulse.

The output transformer 25 is preferably shielded as shown at I? to prevent the starting or stopping impulse, from connecting and disconnecting the high tension 1). C. source I2 to the circuit, fro'm giving a pulse to the circuit I3 and on the line II, which D. C. impulse may cause an erroneous signal to be received at the receiving station. Accordingly the shield I1 electrically separates the primary winding of transformer 24 from its secondary and tertiary windings.

Referring now to Fig. 2 the receiving station of the circuit, the line I I is connected to a transformer I8 provided with a tertiary winding I9 to which is connected rectifier bridge circuit 80. If desired, an amplifier (not shown) may be inserted in the line II prior to the transformer I8.

This receiving circuit comprises a counting chain to an indicating circuit as that is operated j through line 84 when the desired signal has been received and properly stored.

Each one of the undulations received over line I I are transmitted to the counting chain from the secondary winding 85 of transformer I8 through rectifiers 86 and 31' (similar to 31, 38 and 63 in Fig. 1). These pulses, similarly, fire the tubes 38 through 9'! in sequence.

As soon as the first tube 88 is fired, it operates the relay 98 which changes the bias on the cold cathode tube 99 from its normal fixed bias condition through potentiometer comprising resistors I00 connected to the high tension source IOI through line I02, to the receiving bias condition which has substantially the same potential and is provided by the received pulses or signal through the rectifier bridge 80 and now closed contacts I03. In parallel with the tube 99 is provided a time constant circuit comprising condenser I04 which holds the bias for tube 99 a suf- 6 ficient timeto prevent it from'flring between the time that contacts I05 are opened and contacts I03 are closed during the operation of relay 98 and between successive D. C. pulses from the rectifier bridge 80. After the series of pulses corresponding to one digit signal are received, the receiving bias is accordingly removed, after a delay suflicient to discharge condenser I04, since no more energy is applied to the bridge circuit and the tube 93 fires, operating relay I 06. The operation of this relay I06 breaks the normally closed contacts III! which breaks the circuit which maintains relay I08 normally operated. The de-energization of this slow releasing relay I08, opens its contacts I09 which opens the circuit for the de-energization of relays 82, 98 and I06 a sufficient time after ground'is applied-to the conductor 94 through closure of contacts I09 of relay I06 so that the indicating circuit 83 may transfer the signal set up by relays 82: to the desired indicating means before the next signal is received. All of these relays may be operated from a battery I I0 or separate D. C. source (similar to source 23 in Fig. 1).

In the stopping and starting control circuits of Figs. 1 and 2 there are shown spark arresters I I I, each comprising a condenser and a resistor in series.

Referring to the circuit I6 in Fig. 1, if the rectifiers'ZS are not substantially equal in resistance a small compensating resistance (not shown) may be placed in series with the rectifier having'the lower resistance. Furthermore, the difference in these rectifiers 25 may be reduced by making the self inductance of the pri-'- mary winding of transformer 23 as large as possible. The rectification effect of the electronic switch circuit I i may be reduced by increasing the rest value of the direct current, by decreasing the crest of the alternating current source wave, by providing a small input voltage and a high load resistance, and/or by decreasing the resistance of the outward circuit connected to the points 25 and 27. Also, two halves of the magnet c coil in the primary winding of transformer 24 through which the direct current flows, may be'wound over the same portion of the magnetic core to equalize and prevent such D. C. pulses from being transmitted through the transformer. The values of the resistors employed in the circuit M should be properly chosen so that the maximum difference in potential between po nts 26 and 21 will occur each time the conductivity of the circuit is changed.

Although the above system has been described employing cold cathode tubes in the counting chains and control circuits of both the receiving and transmitting station circuits, other types of vacuum tubes, glow or are tubes, including gas filled and grid-glow tubes may be employed.

While I have described above the principles of this invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of this invention.

I claim:

1. A system for transmitting a predetermined number of half waves of alternating electric energy comprising a source of said energy, means to transmit said alternating energy, normally open static switching means having input and output transformers connected through rectifiers, said switching means controlling the connection between said alternating energy source and said transmitting means, a counting chain,

a plurality of controllable switches, each switch corresponding to a diiierent predetermined number of half waves desired to be transmitted, common means actuated by said switches to raise the voltage at said input transformer to close said switching means and to start transmission of said alternating energy, means responsive to the closure of said switch to actuate said counting chain, and means controlled by said counting chain and the operated one of said plurality of switches to raise the voltage at said output transformer above that of said input transformer for opening said switching means to stop said transmission and the operation of said counting chain when said predetermined number of half waves has been transmitted.

2. The system of claim 1 wherein said static switching means includes an electron discharge tube biased to fire when the peak voltage of an alternating energy half wave of a given polarity is added to the biasing voltage and also includes a delay circuit to prevent the opening of said static switching means until the following half wave of opposite polarity commences.

3. A system for transmitting a predetermined number of half waves of alternating electric energy comprising a source of said energy, means to transmit said alternating energy, normally open static switching means having input and output transformers connected through rectifiers, said switching means controlling the connection between said alternating energy source and said transmitting means, a counting chain, a plurality of controllable switches each switch corresponding to a dififerent predetermined number of half waves desired to be transmitted, common means actuated by said switches to raise the voltage of said input transformer to close said switching means to start transmission of said alternating energy, means responsive to the closure of said switch to actuate said counting chain, meanscontrolled by said counting chain and the operated one of said switches to raise the voltage at said output transformer above that at said input transformer for opening said switching means to stop transmission and the operation of said counting chain when said predetermined number of half waves has been transmitted.

4. A normally opened static switch in an alternating electric energy circuit which opens and closes only during the interval between successive substantially whole half-wave undulations of said energy, comprising input and output transformers each having at least a primary and secondary winding, circuit means to connect the secondary of said input transformer in series with the primary of said output transformer, first means responsive to a half wave of a iven polarity of said alternating energy to apply a potential to the mid-point of said input secondary, second means responsive to half wave of a given polarity of said alternating energy to applya potential to the mid-point of said output primary, impedance means in said circuit means blocking the flow of energy from said output mid-point to said input mid-point, means to maintain nor,- mally said output mid-point at a potential sufiiciently above that of said input mid-point to block said alternating energy from flowing through said impedance means, means to actuate said first means to raise the potential at said input mid-point sufilciently above that normally maintained at said output mid-point to permit flow of said alternating energy through said im-- pedance means, means to actuate said second means to raise the potential further at saidoutput mid-point sufficiently to again block said alternating energy from flowing through said impedance means, and means to reset the voltages at said midpoints to their normal levels maintaining said output mid-point voltage sufiiciently above said input mid-point voltage to prevent flow of said alternating energy.

5. The switch of claim 4 wherein said means to actuate said second means is controllably delayed in its operation after the operation of said means to actuate said first means.

6. The switch of claim 4 wherein said first means and second means respectively include tertiary windings in their corresponding transformers.

7. The switch of claim 4 wherein said im pedance means is a rectifier means.

8. The switch of claim 4 including separate delay circuits connected to said mid-points to prevent the rise of voltage of said points until after the half waves which actuate their corresponding first means and second means passes.

ARMAND MAMOR.

REFERENCES CITED The following references are of record in th file of this patent:

UNITED STATES PATENTS Mumma Oct. 19, 1948 

